Vascular vessels are the conduits for circulating blood through a mammalian body. A vascular vessel that carries blood away from a heart is known as an artery. A vascular vessel that returns blood to the heart is known as a vein.
To assist blood flow, veins include venous valves. Each venous valve is located inside a vein and typically includes at least two valve leaflets that are disposed annularly along inside walls of the vein. These valve leaflets open to permit blood flow toward the heart and close, upon a change in pressure, to restrict the back flow or reflux of blood. When blood flows toward the heart, venous pressure forces the valve leaflets to move apart in a downstream flexing motion and create an open path for blood flow. The leaflets normally return to a closed position to restrict or prevent blood flow in a retrograde direction after the venous pressure is relieved. The leaflets, when functioning properly, extend radially inward toward one another such that the leaflet tips contact each other when the valve is closed.
On occasion, and for a variety of reasons including congenital valve or vein weakness, disease in the vein, obesity, pregnancy, or an occupation requiring long periods of standing or sitting, one or more valves in a vein may allow retrograde blood flow to occur. When a valve allows such retrograde flow, blood can collect in vessels beneath the valve and cause an increase in the venous pressure there. Venous valves that allow retrograde flow are known as incompetent venous valves. Incompetent venous valves can cause veins to bulge, can cause swelling in the patient's lower extremities, and can result in varicose veins. If left untreated, varicose veins can result in aching, pain, leg heaviness and swelling, fatigue, and aesthetic issues, among other things.
Surgical and non-surgical methods for treatment of varicose veins exist. An example non-surgical method for treatment of varicose veins is the placement of an elastic stocking around a patient's leg. The stocking can apply external pressure to the vein, forcing the vein walls radially inward and the leaflets into apposition. Another non-surgical treatment method is sclerotherapy, which involves the direct injection of a sclerosing or drug agent solution along the length of the varicose vein using a needle. The chemical solution can irritate the vein tissue, causing the lining of the vein to swell, harden, and eventually seal off.
An example surgical method for treatment of varicose veins includes bringing incompetent leaflets into closer proximity in hopes of restoring natural valve function. Methods for surgical constriction of an incompetent vein can include implanting a frame around the outside of the vessel, placing a constricting suture around the vessel, or other types of treatment to the outside of the vessel to induce vessel contraction. Other surgical treatment methods include: bypassing or replacing damaged venous valves with autologous sections of veins containing competent valves and vein stripping and ligation.
Recently, a number of methods have been suggested to treat varicose veins and venous valve leaflets with energy sources, such as radiofrequency (“RF”) or laser energy. In one such method, valve leaflets can be fastened together with electrodes delivering RF energy. In another such method, a catheter or laser fiber having an electrode tip can be used to apply RF or laser energy to venous wall tissue causing localized heating and corresponding tissue destruction. After treatment of one venous wall section is complete, the catheter or laser fiber can be repositioned to treat a different venous wall section.